Why do people dwell on bad memories? We talk of memories being “scorched” or “branded” into our brains. The phrase “there are just some things you can’t unsee” has gone from being a joke to part of the lexicon
This phenomenon drove Freud, who had written The Pleasure Principle, to write one of his darkest books, in which he moved the furthest from his neurologist roots: Beyond the Pleasure Principle. He considered it “uncanny” (unheimlich) that people would continue to scratch a psychic wound, and speculated about a “deathly” instinct. There seemed to be little he could do for these patients.
An article published in The Best American Science and Nature Writing 2010 looked at recent research on “memory reconsolidation” and sent me in search of the original sources. In short, in remembering something, you (or proteins in your brain) “rewrite” the memory.
Consolidation of memory
For more than 100 years, we’ve known that memories move through an unstable phase to a stable phase, at which time they are said to be consolidated. During the unstable phase, memories can be impaired by distraction or new learning. (They can also be impaired by protein synthesis inhibitors—we’ll get to that in a moment.)
For example, think of trying to remember a phone number. If someone just told you the number and then begins to recite other phone numbers, rattle off random series of numbers, or the phone rings, you’re less likely to remember it. However, if the same reciting, rattling, or ringing occurs the next day, you’ll probably still remember that phone number.
For a long time, that was believed to be that. Memories went through a stabilization or consolidation period, after which they could be “retrieved.” The analogies were always filing cabinets or computers.
Reconsolidation: the present in the past
Then a researcher named Karim Nader conducted a brilliant experiment, published in a letter to the editor of Nature in 2000. Basically, Nader and her group looked at rats that had been trained to associate a tone with a foot shock. When the tone was played, the rats froze in fear.
The next day, the tone was played, and a protein synthesis inhibitor into the amygdala, a part of the brain associated with learned fear. No foot shock followed. The day after that, the tone was played again, and the rats no longer froze in fear. The memory of the initial training was cleared.
Turns out that both the original consolidation of memories and the reconsolidation of memories require protein synthesis. As Nader put it, “Our data show that consolidated fear memories, when reactivated, return to a labile state that requires de novo protein synthesis for reconsolidation.”
Eternal Sunshine of the Spotless Mind? Total Recall? One of those “flashy memory erasing things” from Men in Black?
Not so fast.
But a decade of studies has shown that new learning and other distractions can lead to altered or forgotten memories, but only within a certain window after the memory is brought up. Your mind then lays down a “new” memory, based on current experiences, thoughts, personality, fears, hopes, and dreams.
New hope in post-traumatic stress disorder
Protein synthesis inhibitors used in rat studies are highly toxic, but propanolol (a beta-blocker) may interfere with protein synthesis in the amygdala. That may be why some people report feeling “foggy” when taking this drug.
However, based on the model laid out by Nader, a group looked at what happened if people with post-traumatic stress disorder (PTSD) were asked to recall the traumatic event in detail and then given propanolol. A week later, when asked to remember the traumatic event once more—without propanolol—the researchers measured heart rate, skin conductance (a measure of stress), and the electrical impulses in the “facial frowning” muscle (the left corrugator). All were much, much lower than a group that had received placebo the previous week.
So we’re not in a brave new world of designer memories, memory erasure, or vacations by memory implants. Not just yet. But Freud has been demonstrated wrong (yet again). People with PTSD have been helped. And who knows where this research will lead next?








